Fly ash based shape-stabilized phase change materials for high-temperature thermal energy storage with enhanced thermal conductivity

Molten salt phase change material(PCM) has great potential as a substitute for thermal energy storage, however, their widespread industrial adoption has been limited by issues of leakage. In this study, a shape-stabilized phase change material (SSPCM) with high temperature range (250–800 °C) was successfully synthesized. The fly ash (FA) was employed as the supporting skeleton material, while a ternary sulfate salt composed of Na 2 SO 4 , K 2 SO 4 , and MgSO 4 served as the PCMs. The results indicate that the composite S-FS-45/55 shows excellent chemical compatibility and maintains a stable morphology. The maximum latent heat of the composite reaches 63.10 J/g. After 500 thermal cycles, the composite S-FS-45/55 still maintains excellent chemical compatibility, with a latent heat retention rate of 92.55%. The excellent leakage prevention performance of the SSPCMs may benefit from the reinforcement of the innate mullite-quartz skeleton of the FA during high-temperature sintering process. In addition, the thermal conductivity was increased from 0.33 W/(m·k) to 2.58 W/(m·k) after adding 7.5 wt.% silicon carbide (SiC) in the composite. This study provides a new way for high-value utilization of FA and the design of thermal energy storage materials, demonstrating significant application potential, particularly in the fields of industrial waste heat recovery and clean energy technology.